Estimating the Lateral Location of a Wireless Terminal Based on Temperature and Atmospheric Pressure

ABSTRACT

A technique is disclosed for estimating the lateral location of a wireless terminal in a geographic region. The technique is based on the recognition that some three-dimensional locations of the wireless terminal are improbable, and that measurements of temperature and atmospheric pressure at the wireless terminal and outside can be used to determine which lateral locations of the wireless terminal are improbable.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to “Estimating the Elevation of a WirelessTerminal Based on Temperature and Atmospheric Pressure,” applicationSer. No. 13/______,______, Attorney Docket 465-365us1, which isincorporated by reference in its entirety.

This application claims the benefit under 35 U.S.C. §119(e) to“Smartphone Absolute Altitude Estimation Using Barometer Data,”Provisional Application Ser. No. 62/033,968, Attorney Docket 465-364pr1,which is incorporated by reference in its entirety.

This application is related to U.S. Pat. Nos. 6,518,918, 6,944,465,7,460,505, 7,383,051, 7,257,414, 7,753,278, 7,433,695, 7,848,762, and8,306,676, and 8,630,665, each of which are incorporated by reference.

This application is related to U.S. Patent Application Publications2008/0077356, 2008/0077472, and 2008/0077516, each of which areincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to telecommunications in general, and,more particularly, to a technique for estimating the location of awireless terminal based on the temperature and atmospheric pressure inthe vicinity of the wireless terminal.

BACKGROUND OF THE INVENTION

The salient advantage of wireless telecommunications over wirelinetelecommunications is the user of the wireless terminal is afforded theopportunity to use his or her terminal anywhere. On the other hand, thesalient disadvantage of wireless telecommunications lies in that factthat because the user is mobile, an interested party might not be ableto readily ascertain the location of the user.

Such interested parties might include both the user of the wirelessterminal and a remote party. There are a variety of reasons why the userof a wireless terminal might be interested in knowing his or herlocation. For example, the user might be interested in telling a remoteparty where he or she is or, alternatively, the user might seek advicein navigation.

In addition, there are a variety of reasons why a remote party might beinterested in knowing the location of the user. For example, therecipient of an E 9-1-1 emergency call from a wireless terminal might beinterested in knowing the location of the wireless terminal so thatemergency services vehicles can be dispatched to that location.

There are many techniques in the prior art for estimating the locationof a wireless terminal. In accordance with some techniques, the locationof a wireless terminal is estimated, at least in part, from signalmeasurements that are reported by the wireless terminal. The reportedmeasurements are of signals measured by the wireless terminal that aretransmitted by one or more base stations and, in some cases, by GlobalPositioning System (GPS) satellites. In order for these techniques towork, at least some of the transmitted signals have to be strong enoughto allow for accurate measurement by the wireless terminal and forreliable processing by the particular estimation technique. Some ofthese techniques work well even in environments where the measuredstrengths of the different signals vary significantly, such as wheresignal obstructions are present, including natural obstructions such asmountains and artificial obstructions such as buildings.

SUMMARY OF THE INVENTION

There are many techniques in the prior art that for generating anestimate of the location of a wireless terminal, and each technique hasits advantages and disadvantages.

For example, the cost of generating a location estimate—in terms oftime, hardware, money, compute cycles, and energy—depends on thetechnique and on the quantity and quality of the empirical data. Thereare some techniques in which the cost of generating a location estimateis approximately constant regardless of the quantity and quality of theempirical data. This is particularly true for geometry-based techniquessuch as the Global Positioning System andObserved-Time-Difference-of-Arrival.

In contrast, there are some techniques in which the cost of a locationestimate can vary widely based on the quantity and quality of theempirical data. This is particularly true for pattern-matchingtechniques such as Radio-Frequency Pattern Matching. For thesetechniques, it is advantageous to employ, when possible, mechanisms thatlower the average (or maximum) cost of an estimate. The presentinvention, as recited in the claims, is one such mechanism.

The illustrative embodiment of the present invention exploits:

-   -   (i) measurements of temperature and atmospheric pressure        outdoors,    -   (ii) measurements of temperature and atmospheric pressure at the        wireless terminal, and    -   (iii) knowledge of the terrain, buildings, and other structures        to both:    -   (i) reduce the cost of a location estimate, and    -   (ii) improve the accuracy of the location estimate.

This is accomplished by recognizing that some estimates of the locationof a wireless terminal in three-dimensional space are improbable, andthat measurements of temperature and atmospheric pressure can be used toquickly and inexpensively eliminate from consideration locations thatare—in a given circumstance—improbable.

For example, when a wireless terminal is known to be in downtownWashington, D.C., and a measurement of atmospheric pressure at awireless terminal suggests that the wireless terminal is at an elevationof 180 meters above mean sea level, the illustrative embodiment canreasonably designate every possible lateral location of the wirelessterminal as improbable except for the Washington Monument (whose tip isat an elevation above mean sea level of approximately 198 meters).

Thus, the illustrative embodiment improves the accuracy of the locationestimate by eliminating the possibility of making an error by estimatingthat the lateral location of the wireless terminal as at the WhiteHouse. Furthermore, the illustrative embodiment lowers the cost of thelocation estimate by quickly eliminating the need to expend resources toconsider lateral locations other than the Washington Monument.

The illustrative embodiment comprises: A method of estimating thelateral location of a wireless terminal, the method comprising:receiving, at a data processing system, the identity of a radio signalthat is received by a wireless terminal; receiving, at the dataprocessing system, a measurement of atmospheric pressure at the wirelessterminal; designating at least one of a plurality of possible laterallocations of the wireless terminal as improbable based on: (i) themeasurement of atmospheric pressure at the wireless terminal; andestimating the lateral location of the wireless terminal to be one ofthe plurality of possible lateral locations of the wireless terminal notdesignated as improbable based on: (i) the identity of the radio signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a diagram of the salient components of wirelesstelecommunications system 100 in accordance with the illustrativeembodiment of the present invention.

FIG. 2 depicts a block diagram of the salient components of wirelessterminal 101 in accordance with the illustrative embodiment of thepresent invention.

FIG. 3 depicts a block diagram of the salient components of locationengine 113 in accordance with the illustrative embodiment.

FIG. 4 depicts a flowchart of the salient processes performed inaccordance with the illustrative embodiment of the present invention.

FIG. 5 depicts a flowchart of the salient processes performed inaccordance with task 401.

FIG. 6 depicts an isometric drawing of geographic region 120 inaccordance with the illustrative embodiment of the present invention.

FIG. 7 a detailed map of the ground level of geographic region 120.

FIG. 8 depicts geographic region 120 divided into a 10 by 10 grid.

FIG. 9 depicts a map that depicts where in geographic region 120 it isnot improbable for wireless terminal 101 to be located.

FIG. 10 depicts a flowchart of the salient processes performed inaccordance with task 402.

FIG. 11 depicts a flowchart of the salient processes performed inaccordance with task 403.

FIG. 12 depicts a flowchart of the salient processes performed inaccordance with task 404.

FIG. 13 depicts an illustrative map of the lateral locations ingeographic region 120 that are designated as improbable and those thatare not.

DEFINITIONS

Atmospheric Pressure—For the purposes of this specification, the term“atmospheric pressure” is defined as the force per unit area exerted ona surface by the weight of the air above that surface in the atmosphereof Earth.

Based on—For the purposes of this specification, the phrase “based on”is defined as “being dependent on” in contrast to “being independentof”. The value of Y is dependent on the value of X when the value of Yis different for two or more values of X. The value of Y is independentof the value of X when the value of Y is the same for all values of X.Being “based on” includes both functions and relations.

Elevation—For the purposes of this specification, the term “elevation”is defined as the height above or below a fixed reference point (e.g.,standard sea level, ground level, etc.).

Generate—For the purposes of this specification, the infinitive “togenerate” and its inflected forms (e.g., “generating”, “generation”,etc.) should be given the ordinary and customary meaning that the termswould have to a person of ordinary skill in the art at the time of theinvention.

Height—For the purposes of this specification, the term “height” shouldbe given the ordinary and customary meaning that the term would have toa person of ordinary skill in the art at the time of the invention.

Identity of a Radio Signal—For the purposes of this specification, thephrase “identity of a radio signal” is defined as one or more indiciathat distinguish one radio signal from another radio signal.

Lateral Location—For the purposes of this specification, a “laterallocation” is defined as information that is probative of latitude orlongitude or latitude and longitude.

Location—For the purposes of this specification, the term “location” isdefined as a zero-dimensional point, a finite one-dimensional pathsegment, a finite two-dimensional surface area, or a finitethree-dimensional volume.

Location-Dependent Trait of a Radio Signal—For the purposes of thisspecification, the term “location-dependent trait of a radio signal” isdefined as a characteristic of a radio signal that varies with:

(i) the location of the transmitter of the signal, or

(ii) the location of the receiver of the signal, or

(iii) both i and ii.

For example and without limitation, the amplitude and phase of a radiosignal are generally location-dependent traits of the signal. Incontrast, the frequency of a radio signal is generally not alocation-dependent trait of the signal.

Location-Trait Database—For the purposes of this specification, a“Location-Trait Database” is defined as a mapping that associates:

-   -   (i) one or more location-dependent traits of one or more radio        signals received or transmitted by a wireless terminal, or    -   (ii) the identity of one or more radio signals received or        transmitted by a wireless terminal, or    -   (iii) both i and ii, at each of a plurality of locations.

Processor—For the purposes of this specification, a “processor” isdefined as hardware or hardware and software that performs mathematicaland/or logical operations.

Radio—For the purposes of this specification, a “radio” is defined ashardware or hardware and software that is capable of telecommunicationsvia an unguided (i.e., wireless) radio signal of frequency less than 600GHz.

Receive—For the purposes of this specification, the infinitive “toreceive” and its inflected forms (e.g., “receiving”, “received”, etc.)should be given the ordinary and customary meaning that the terms wouldhave to a person of ordinary skill in the art at the time of theinvention.

Transmit—For the purposes of this specification, the infinitive “totransmit” and its inflected forms (e.g., “transmitting”, “transmitted”,etc.) should be given the ordinary and customary meaning that the termswould have to a person of ordinary skill in the art at the time of theinvention.

Wireless terminal—For the purposes of this specification, the term“wireless terminal” is defined as a device that is capable oftelecommunications without a wire or tangible medium. A wirelessterminal can be mobile or immobile. A wireless terminal can transmit orreceive or transmit and receive. As is well known to those skilled inthe art, a wireless terminal is also commonly called a cell phone, apager, a wireless transmit/receive unit (WTRU), a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, and any othertype of device capable of operating in a wireless environment areexamples of wireless terminals.

DETAILED DESCRIPTION

FIG. 1 depicts a diagram of the salient components of wirelesstelecommunications system 100 in accordance with the illustrativeembodiment of the present invention. Wireless telecommunications system100 comprises: wireless terminal 101, cellular base stations 102-1,102-2, and 102-3, Wi-Fi base stations 103-1 and 103-2, wirelessinfrastructure 111, location-based application server 112, locationengine 113, weather station 114, and GPS constellation 121, interrelatedas shown.

Wireless infrastructure 111, location-based application server 112,location engine 113, weather station 114, and Wi-Fi base stations 103-1and 103-2 are all connected to one or more interconnected computernetworks (e.g., the Internet, a local-area network, a wide-area network,etc.) and, as such, can exchange data in well-known fashion.

Although the illustrative embodiment depicts wireless telecommunicationssystem 100 as comprising only one wireless terminal, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention that comprise anynumber of wireless terminals.

Wireless terminal 101 comprises the hardware and software necessary toperform the processes described below and in the accompanying figures.Furthermore, wireless terminal 101 is mobile and can be at any locationwithin geographic region 120 at any time.

Wireless terminal 101 is capable of providing bi-directional voice,data, and video telecommunications service to a user (not shown), but itwill be clear to those skilled in the art, after reading thisdisclosure, how to make and use embodiments of the present invention inwhich wireless terminal 101 provides a different set of services.

In accordance with the illustrative embodiment, wireless terminal 101 iscapable of receiving one or more radio signals from each of basestations 102-1, 102-2, and 102-3, Wi-Fi base stations 103-1 and 103-2,and GPS constellation 121, in well-known fashion. Wireless terminal 101is also capable of identifying each radio signal it receives, inwell-known fashion, and of transmitting the identity of each signal itreceives to location engine-113. Wireless terminal 101 is furthercapable of measuring one or more location-dependent traits of each radiosignal it receives, in well-known fashion, and of transmitting eachmeasurement it generates to location engine 113. And still furthermore,wireless terminal 101 is capable of measuring a difference of alocation-dependent trait of two signals it receives, in well-knownfashion, and of transmitting such measurements to location engine 113.

In accordance with the illustrative embodiment, wireless terminal 101 iscapable of transmitting one or more radio signals—that can be receivedby one or more of base stations 102-1, 102-2, and 102-3 and Wi-Fi basestations 103-1 and 103-2—in accordance with specific parameters (e.g.,signal strength, frequency, coding, modulation, etc.), in well-knownfashion, and of transmitting those parameters to location engine 113.

In accordance with the illustrative embodiment, and as described indetail below, wireless terminal 101 comprises a barometer 205 (shown inFIG. 2) and thermometer 206 (also shown in FIG. 2). Wireless terminal101 is capable of measuring (periodically, sporadically, and on-demand)the atmospheric pressure and temperature, in well-known fashion, and oftransmitting the measurements to location engine 113.

Cellular base stations 102-1, 102-2, and 102-3 communicate with wirelessinfrastructure 111 via wireline and with wireless terminal 101 via radioin well-known fashion. As is well known to those skilled in the art,base stations are also commonly referred to by a variety of alternativenames such as access points, nodes, network interfaces, etc. Althoughthe illustrative embodiment comprises three base stations, it will beclear to those skilled in the art, after reading this disclosure, how tomake and use alternative embodiments of the present invention thatcomprise any number of base stations.

In accordance with the illustrative embodiment of the present invention,cellular base stations 102-1, 102-2, and 102-3 are terrestrial,immobile, and base station 102-3 is within geographic region 120. Itwill be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which some or all of the base stations are airborne,marine-based, or space-based, regardless of whether or not they aremoving relative to the Earth's surface, and regardless of whether or notthey are within geographic region 120.

Cellular base stations 102-1, 102-2, and 102-3 comprise the hardware andsoftware necessary to be 3GPP-compliant and to perform the processesdescribed below and in the accompanying figures. For example and withoutlimitation, each of cellular base stations 102-1, 102-2, and 102-3 arecapable of continually:

-   -   a. receiving one or more radio signals transmitted by wireless        terminal 101, and    -   b. identifying each radio signal transmitted by wireless        terminal 101, in well-known fashion, and of transmitting the        identity of those signals to location engine 113, and    -   c. measuring one or more location-dependent traits of each radio        signal transmitted by wireless terminal 101, in well-known        fashion, and of transmitting the measurements to location engine        113, and    -   d. transmitting one or more signals to wireless terminal 101 in        accordance with specific parameters (e.g., signal strength,        frequency, coding, modulation, etc.), in well-known fashion, and        of transmitting those parameters to location engine 113.        It will be clear to those skilled in the art how to make and use        cellular base stations 102-1, 102-2, and 102-3.

Wi-Fi base stations 103-1 and 103-2 communicate with wireless terminal101 via radio in well-known fashion. Wi-Fi base stations 103-1 and 103-2are terrestrial, immobile, and within geographic region 120. Althoughthe illustrative embodiment comprises two Wi-Fi base stations, it willbe clear to those skilled in the art, after reading this disclosure, howto make and use alternative embodiments of the present invention thatcomprise any number of Wi-Fi base stations.

Each of Wi-Fi base stations 103-1 and 103-2 are capable of continually:

-   -   a. receiving one or more radio signals transmitted by wireless        terminal 101, and    -   b. identifying each radio signal transmitted by wireless        terminal 101, in well-known fashion, and of transmitting the        identity of those signals to location engine 113, and    -   c. measuring one or more location-dependent traits of each radio        signal transmitted by wireless terminal 101, in well-known        fashion, and of transmitting the measurements to location engine        113, and    -   d. transmitting one or more signals to wireless terminal 101 in        accordance with specific parameters (e.g., signal strength,        frequency, coding, modulation, etc.), in well-known fashion, and        of transmitting those parameters to location engine 113.

It will be clear to those skilled in the art how to make and use Wi-Fibase stations 103-1 and 103-2.

Wireless infrastructure 111 comprises a switch that orchestrates theprovisioning of telecommunications service to wireless terminal 101 andthe flow of information to and from location engine 113, as describedbelow and in the accompanying figures. As is well known to those skilledin the art, wireless switches are also commonly referred to by othernames such as mobile switching centers, mobile telephone switchingoffices, routers, etc.

Location-based application server 112 comprises hardware and softwarethat uses the estimate of the location of wireless terminal101—generated by location engine 113—in a location-based application, inwell-known fashion. Location-based applications are well-known in theart and provide services such as without limitation E-911 routing,navigation, location-based advertising, weather alerts.

Location engine 113 is a data processing system that comprises hardwareand software that generates one or more estimates of the location ofwireless terminal 101 as described below and in the accompanyingfigures. It will be clear to those skilled in the art, after readingthis disclosure, how to make and use location engine 113. Furthermore,although location engine 113 is depicted in FIG. 2 as physicallydistinct from wireless infrastructure 111, it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments of the present invention in which locationengine 113 is wholly or partially integrated into wirelessinfrastructure 111. Location engine 113 comprises the location-traitdatabase and GIS databases, which are described in detail below.

Weather station 114 comprises hardware and software that continuallymeasures the outdoor temperature and atmospheric pressure, in well-knownfashion, and transmits those measurements to location engine 113.Weather station 114 is at a known location in geographic region andknown elevation. Although the illustrative embodiment comprises only oneweather station, it will be clear to those skilled in the art how tomake and use alternative embodiments of the present invention thatcomprise any number of weather stations.

FIG. 2 depicts a block diagram of the salient components of wirelessterminal 101 in accordance with the illustrative embodiment of thepresent invention. Wireless terminal 101 comprises: radio receiver andtransmitter 201, processor 202, memory 203, human interface 204,barometer 205, and thermometer 206, interconnected as shown.

Radio receiver and transmitter 201 comprises hardware and software thatenables wireless terminal 101 to receive (and analyze) radio signals andto transmit radio signals. In accordance with the illustrativeembodiment, wireless telecommunications service is provided to wirelessterminal 101 in accordance with the air-interface standard of the 3^(rd)Generation Partnership Project (“3GPP”). After reading this disclosure,however, it will be clear to those skilled in the art how to make anduse alternative embodiments of the present invention that operate inaccordance with one or more other air-interface standards (e.g., GlobalSystem Mobile “GSM,” UMTS, CDMA-2000, IS-136 TDMA, IS-95 CDMA, 3GWideband CDMA, IEEE 802.11 Wi-Fi, 802.16 WiMax, Bluetooth, etc.) in oneor more frequency bands. As will be clear to those skilled in the art, awireless terminal is also known as a “cell phone,” “mobile station,”“car phone,” “PDA,” and the like. It will be clear to those skilled inthe art how to make and use radio receiver and transmitter 201.

Processor 202 is hardware under the command of software stored in memory203 that performs all of the functions described below and in theaccompanying figures. It will be clear to those skilled in the art howto make and use processor 202.

Memory 203 is a non-volatile random-access memory that holds all of theprogramming and data required for the operation of wireless terminal101. It will be clear to those skilled in the art how to make and usememory 203.

Human interface 204 is hardware and software that enables a person tointeract with wireless terminal 101. Human interface 204 comprises adisplay, keypad, microphone, and speaker, and it will be clear to thoseskilled in the art how to make and use human interface 204.

Barometer 205 is a hardware MEMS sensor that measures the atmosphericpressure at wireless terminal 101. In accordance with the illustrativeembodiment, barometer 205 is the LSP331AP MEMS pressure sensor from STMicroelectronics, but it will be clear those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention that use a different sensor to measure theatmospheric pressure.

Thermometer 206 is a hardware temperature sensor that measures theambient temperature at wireless terminal 101. In accordance with theillustrative embodiment, thermometer 206 is the ADT7420 temperaturesensor from Analog Devices, but it will be clear to those skilled in theart, after reading this disclosure, how to make and use alternativeembodiments of the present invention that use a different sensor tomeasure the ambient temperature at wireless terminal 101.

Radio receiver and transmitter 201 are capable of performing theprocesses described below and in the accompanying figures. For exampleand without limitation, wireless terminal 101 is capable of:

-   -   a. receiving one or more radio signals transmitted by cellular        base stations 102-1, 102-2, and 102-3, Wi-Fi base stations 103-1        and 103-2, and GPS constellation 121, and    -   b. identifying each radio signal transmitted by cellular base        stations 102-1, 102-2, and 102-3, Wi-Fi base stations 103-1 and        103-2, and GPS constellation 121, in well-known fashion, and of        transmitting the identity of those signals to location engine        113, and    -   c. measuring one or more location-dependent traits of each radio        signal transmitted by cellular base stations 102-1, 102-2, and        102-3, Wi-Fi base stations 103-1 and 103-2, and GPS        constellation 121, in well-known fashion, and of transmitting        the measurements to location engine 113, and    -   d. transmitting one or more signals to cellular base stations        102-1, 102-2, and 102-3, Wi-Fi base stations 103-1 and 103-2 in        accordance with specific parameters (e.g., signal strength,        frequency, coding, modulation, etc.), in well-known fashion, and        of transmitting those parameters to location engine 113, and    -   e. measuring the temperature and atmospheric pressure at        wireless terminal 101, in well-known fashion, and transmitting        those measurements to location engine 113.        It will be clear to those skilled in the art how to make and use        wireless terminal 101.

Location Engine 113—

FIG. 3 depicts a block diagram of the salient components of locationengine 113 in accordance with the illustrative embodiment. Locationengine 113 comprises: processor 301, memory 302, and receiver andtransmitter 303, which are interconnected as shown.

Processor 301 is a general-purpose processor that is capable ofexecuting an operating system, the application software that performstasks 402 through 406 (described herein and shown in FIG. 4), and ofpopulating, amending, using, and managing a location-trait database anda GIS database, as described in detail below and in the accompanyingfigures. It will be clear to those skilled in the art how to make anduse processor 301.

In general, the location-trait database contains information for thepossible locations of wireless terminal and the identity andlocation-dependent traits of radio signals as if wireless terminal 101were at each of those locations. It will be clear to those skilled inthe art how to make and use the location-trait database.

In general, the GIS database contains information for geographic region120, including without limitation, the physical characteristics of allof the structures in geographic region 120. It will be clear to thoseskilled in the art how to make and use the GIS database.

Memory 302 is a non-volatile memory that stores:

a. the operating system, and

b. the application software, and

c. the location-trait database, and

d. the GIS database.

It will be clear to those skilled in the art how to make and use memory302.

Receiver and transmitter 303 enables location engine 113 to transmit toand receive from wireless terminal 101, wireless infrastructure 111,location-based application server 112, weather station 114, and Wi-Fibase stations 103-1 and 103-2, in well-known fashion. It will be clearto those skilled in the art how to make and use receiver and transmitter303.

Operation of the Illustrative Embodiment—

FIG. 4 depicts a flowchart of the salient processes performed inaccordance with the illustrative embodiment of the present invention.

At task 401, the location-trait database and the GIS database areconstructed and stored in memory 302 of location engine 113. Task 401 isdescribed in detail below and in the accompanying figures.

At task 402, location engine 113 collects measurements of temperatureand atmospheric pressure from weather station 114 and wireless terminal101. Task 402 is described in detail below and in the accompanyingfigures.

At task 403, location engine 113 collects empirical data on the radiosignals received and transmitted by wireless terminal 101. Task 403 isdescribed in detail below and in the accompanying figures.

At task 404, location engine 113 designates at least one of a pluralityof possible lateral locations of wireless terminal 101 as improbablebased on:

-   -   (i) the measurements of temperature and atmospheric pressure        received in task 402, and    -   (ii) the information in the GIS database.        Task 404 is described in detail below and in the accompanying        figures.

At task 405, location engine 113 generates an estimate of the laterallocation of wireless terminal 101 based on:

-   -   (i) the plurality of possible lateral locations not designated        as improbable in task 404,    -   (ii) the empirical data on radio signals received in task 403,        and    -   (iii) the information in the location-trait database.        It will be clear to those skilled in the art how to enable        embodiments of the present invention to perform task 405. See        for example and without limitation, U.S. Pat. Nos. 6,944,465,        7,460,505, 7,383,051, 7,257,414, 7,753,278, 7,433,695,        7,848,762, and 8,630,665, each of which are incorporated by        reference.

At task 406, location engine 113 transmits:

-   -   (i) the estimate of the lateral location of wireless terminal        101 generated in task 405, and    -   (ii) the estimate of the elevation of wireless terminal 101        generated in task 404        to location-based application server 112 and to wireless        terminal 101 for use in a location-based application. It will be        clear to those skilled in the art how to enable embodiments of        the present invention to perform task 406. After task 406 is        completed, control passes back to task 402.

Task 401: Construct the GIS Database and the Location-Trait Database—

FIG. 5 depicts a flowchart of the salient processes performed inaccordance with task 401.

At task 501, the GIS database is constructed and stored in memory 302 oflocation engine 113.

As part of task 501, geographic region 120 is delimited and surveyed inthree dimensions. FIG. 6 depicts an isometric drawing of geographicregion 120, which spans approximately four city blocks and comprises,among other things, park 601, boxy building 602, empty lot 603, andcylindrical building 604. It will be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments of the present invention that comprise any area, anygeographic features, and any number, size, height, and shape ofstructures.

In accordance with the illustrative embodiment, geographic region 120 isflat, level, and at an elevation of 1000 meters. It will be clear tothose skilled in the art, however, after reading this disclosure, how tomake and use alternative embodiments of the present invention in whichgeographic region is not flat, not level, and/or is at a differentelevation.

In accordance with the illustrative embodiment, the height of boxybuilding 602 is 128 meters and the height of cylindrical building 604 is140 meters. In other words, the elevation of boxy building 602 is 1128meters and the elevation of cylindrical building 604 is 1140 meters. Itwill be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which the structures have any height.

In accordance with the illustrative embodiment, geographic region 120 issquare and comprises approximately four city blocks of an urbanenvironment. It will be clear to those skilled in the art however, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention in which geographic region 120 has any area of anyshape and any population density and development. As part of task 501, adetailed map of the ground level of geographic region is made inwell-known fashion, and as shown in FIG. 7.

As part of task 501, grid 800 is overlaid onto geographic region 120 asshown in FIG. 8. Grid 800 is an 10 by 10 grid that partitions geographicregion 120 into a plurality of possible lateral locations of wirelessterminal 101. FIG. 8 also depicts the relationship of the footprints ofboxy building 602 and cylindrical building 604 with respect to the grid.

Although the illustrative embodiment comprises 100 grid squares, it willbe clear to those skilled in the art how to make and use alternativeembodiments of the present invention that comprise any number ofpossible lateral locations with any shape. See for example and withoutlimitation, U.S. Pat. No. 7,753,278, which is incorporated by reference.

At any instant, the three-dimensional location of wireless terminal 101can be described by a combination of a lateral location and anelevation. Although it is not improbable for wireless terminal 101 to beat any lateral location in geographic region 120 and it is notimprobable for wireless terminal 101 to be at any elevation (up to 140meters) above geographic region 120, it is improbable for wirelessterminal 101 to be at some combinations of those lateral locations andelevations. For example, it is not improbable for wireless terminal 101to be at a lateral location in park 601 and to have an elevation of 1001meters (i.e., be at or near ground level). It is, however, improbablefor wireless terminal 101 to be at a lateral location in park 601 and tohave an elevation of 1060 meters.

Therefore, as part of task 501, each improbable combination of laterallocations and elevations for wireless terminal 101 in geographic regionis determined, indexed by elevation, and stored in the GIS database.Each improbable combination of lateral locations and elevation forwireless terminal 101 can be determined by referencing thethree-dimensional survey of geographic region 120, which is depicted inFIG. 9.

From the survey (as depicted in FIGS. 8 and 9), it can be easily seenthat when wireless terminal 101 is at ground level (e.g., under anelevation of 1003 meters, etc.), it is not improbable for wirelessterminal 101 to be at any lateral location in geographic region 120.

In contrast, when wireless terminal 101 is at an elevation above groundlevel (e.g., above an elevation of 1003 meters, etc.) and below therooftop of building 602 (1128 meters), it is improbable for wirelessterminal 101 to be at any lateral location that is outside of eitherboxy building 602 or cylindrical building 604. Therefore, when wirelessterminal 101 is in this range of elevations, the plurality of laterallocations of wireless terminal 101 that are not improbable include:(6,2), (6,3), (6,5), (6,6), (6,7), (7,2), (7,3), (7,5), (7,6), and(7,7).

When wireless terminal 101 is at an elevation above the rooftop ofbuilding 602 (1128 meters) and below the rooftop of building 604 (1140meters), it is improbable for wireless terminal 101 to be at any laterallocation that is outside of cylindrical building 604. Therefore, whenwireless terminal 101 is in this range of elevations, the plurality oflateral locations of wireless terminal 101 that are not improbableinclude: (6,5), (6,6), (6,7), (7,5), (7,6), and (7,7).

This information is stored in the GIS database in memory 302 as shown inTable 1.

TABLE 1 Possible Lateral Locations of Wireless Terminal 101 That Are NotImprobable Given The Elevation of Wireless Terminal 101 Possible LateralLocations of Wireless Elevation of Wireless Terminal 101 That Terminal101 Are Not Improbable 1000 to 1003 meters All 100 Grid Squares 1003 to1128 meters (6, 2), (6, 3), (6, 5), (6, 6), (6, 7), (7, 2), (7, 3), (7,5), (7, 6), (7, 7) 1028 to 1140 meters (6, 5), (6, 6), (6, 7), (7, 5),(7, 6), (7, 7)

At task 502, the location-trait database is constructed and stored intomemory 302 of location engine 113. As part of task 503, the identity—andlocation-dependent traits for—each radio signal that wireless terminalis expected to be able to receive from cellular base stations 102-1,102-2, and 102-3, Wi-Fi base stations 103-1 and 103-2, for each possiblelateral location of wireless terminal 101, is determined in well-knownfashion.

As part of task 502, the identity of—and location-dependent traitsfor—each radio signal that each of cellular base stations 102-1, 102-2,and 102-3, Wi-Fi base stations 103-1 and 103-2 is expected to be able toreceive from wireless terminal 101, for each possible lateral locationof wireless terminal 101, is determined in well-known fashion.

It will be clear to those skilled in the art how to accomplish task 503,and in accordance with the illustrative embodiment, this is accomplishedthrough a combination of “drive testing” (i.e., empirical datagathering) and radio-frequency propagation modeling. See for example andwithout limitation, U.S. Patent Application Publications 2008/0077356,2008/0077472, and 2008/0077516, which are incorporated by reference.

Task 402: Collect Temperature and Atmospheric Measurements—

FIG. 10 depicts a flowchart of the salient processes performed inaccordance with task 402.

At task 1001, weather station 114 transmits a measurement oftemperature, T_(W), and a measurement of atmospheric pressure, P_(W), tolocation engine 113. In accordance with the illustrative embodiment,task 1001 is performed every 10 minutes, but it will be clear to thoseskilled in the art how to make and use alternative embodiments of thepresent invention that transmit the measurements at other times.

At task 1002, location engine 113 receives the measurement oftemperature, T_(W), and a measurement of atmospheric pressure, P_(W),transmitted in task 1101.

At task 1003, wireless terminal 101 transmits a measurement oftemperature, T_(T), and a measurement of atmospheric pressure, P_(T), tolocation engine 113. In accordance with the illustrative embodiment,task 1003 is performed every 5 seconds, but it will be clear to thoseskilled in the art how to make and use alternative embodiments of thepresent invention that transmit the measurements at other times.

At task 1004, location engine 113 receives the temperature andatmospheric measurements transmitted in task 1103.

In accordance with the illustrative embodiment, tasks 1001, 1002, 1003,and 1004 are performed continuously, concurrently, and asynchronously.

Task 403: Collect Empirical Data on Radio Signals—

FIG. 11 depicts a flowchart of the salient processes performed inaccordance with task 403.

At task 1101, each of cellular base stations 102-1, 102-2, and 102-3 andWi-Fi base stations 103-1 and 103-2 transmits the identity of eachsignal it has received from wireless terminal 101 and the measurementsof the location-dependent traits of those signals. In accordance withthe illustrative embodiment, task 1101 is performed every 20milliseconds, but it will be clear to those skilled in the art how tomake and use alternative embodiments of the present invention thattransmit the measurements at other times.

At task 1102, location engine receives the identities and measurementstransmitted at task 1101.

At task 1103, wireless terminal 101 transmits the identity of eachsignal it receives from cellular base stations 102-1, 102-2, and 102-3and Wi-Fi base stations 103-1 and 103-2 and the measurements of thelocation-dependent traits of those signals. In accordance with theillustrative embodiment, task 1103 is performed every 20 milliseconds,but it will be clear to those skilled in the art how to make and usealternative embodiments of the present invention that transmit themeasurements at other times.

At task 1104, location engine receives the identities and measurementstransmitted at task 1103.

In accordance with the illustrative embodiment, tasks 1101, 1102, 1103,and 1104 are performed continuously, concurrently, and asynchronously.

Task 404: Designate at Least One of the Plurality of Possible LateralLocations of Wireless Terminal as Improbable Based on the Measurementsof Temperature and Atmospheric Pressure—

FIG. 12 depicts a flowchart of the salient processes performed inaccordance with task 404.

At task 1201, location engine 113 generates an estimate of the referenceatmospheric pressure for geographic location 120, P₀, based on:

$\begin{matrix}{P_{0} = \frac{P_{W}}{^{- {(\frac{Z_{W}}{H})}}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

wherein:

-   -   P₀ is the reference atmospheric pressure for geographic location        120,    -   P_(W) is the Measurement of Atmospheric Pressure Received from        weather station 114 that most closely corresponds in time to the        measurement of atmospheric pressure of interest received from        wireless terminal 101, P_(T),    -   Z_(W) is the elevation of weather station 114 (1000 meters in        the illustrative embodiment), and    -   H is the scale height of the atmosphere, which is the elevation        at which the atmospheric pressure has decreased to e⁻¹ times its        value at mean sea level (e.g., approximately 7000 meters).

At task 1202, location engine 113 generates an estimate of the elevationof wireless terminal 101, Z_(T), based on:

$\begin{matrix}{Z_{T} = {{- H}\; {\ln \left( \frac{P_{T}}{P_{0}} \right)}}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

wherein:

-   -   P_(T) is the relevant measurement of atmospheric pressure        received from wireless terminal 101.

At task 1203, location engine 113 generates an estimate of the margin oferror in the estimate of elevation, Z_(T), which—if wireless terminal101 is inside of a building—might be caused by the stack effect. Themargin of error, E, is based on:

$\begin{matrix}{E = {{{{- H}\; {\ln \left( \frac{P_{T} - P_{M}}{P_{0}} \right)}} - Z_{T}}}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

wherein:

-   -   P_(M) is the maximum pressure differential that might be caused        by the stack effect if wireless terminal 101 is inside of a        building, which is found by:

$\begin{matrix}{P_{M} = {{CBP}_{W}\left( {\frac{1}{T_{W}} - \frac{1}{T_{T}}} \right)}} & \left( {{Eq}.\mspace{14mu} 4} \right)\end{matrix}$

wherein:

-   -   C is a constant equal to 0.0342 (for SI units) and 0.0188 (for        U.S. units),    -   B is the height of the tallest structure in geographic region        120,    -   P_(W) is the measurement of atmospheric pressure at weather        station 114,    -   T_(W) is the measurement of temperature at weather station 114,        and    -   T_(T) is the measurement of temperature at wireless terminal        101.

Considering the maximum possible error caused by the stack effect, therange of possible elevations for wireless terminal 101 is any elevationZ_(T)−E between Z_(T)+E, exclusively.

At task 1203, location engine 113 designates at least one of a pluralityof possible lateral locations of wireless terminal 101 as improbablebased on the estimate of the elevation of wireless terminal 101. This isaccomplished by designating all of the possible lateral locations ofwireless terminal 101 as improbable except for those corresponding inTable 1 to any elevation Z_(T)−E between Z_(T)+E, exclusively.

For example, if the value of Z_(t) is 1127 meters and E=4 meters thenZ_(T)−E=1124 meters and Z_(T)+E=1131 meters. All 100 grid squares ingrid 800 are designated as improbable except for the ten grid squarescorresponding to 1124 meters—(6,2), (6,3), (6,5), (6,6), (6,7), (7,2),(7,3), (7,5), (7,6), and (7,7)—or the six grid squares corresponding to1131 meters—(6,5), (6,6), (6,7), (7,5), (7,6), and (7,7) or both. Inthis case, other 90 grid squares are designated as improbable, as shownin FIG. 13.

It is to be understood that the disclosure teaches just one example ofthe illustrative embodiment and that many variations of the inventioncan easily be devised by those skilled in the art after reading thisdisclosure and that the scope of the present invention is to bedetermined by the following claims.

What is claimed is:
 1. A method of estimating the lateral location of awireless terminal, the method comprising: receiving, at a dataprocessing system, the identity of a radio signal that is received by awireless terminal; receiving, at the data processing system, ameasurement of atmospheric pressure at the wireless terminal;designating at least one of a plurality of possible lateral locations ofthe wireless terminal as improbable based on: (i) the measurement ofatmospheric pressure at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the identity of the radio signal.
 2. The methodof claim 1 further comprising: receiving, at the data processing system,a measurement of a location-dependent trait of a radio signal asreceived by the wireless terminal; and wherein estimating the laterallocation of the wireless terminal to be one of the plurality of possiblelateral locations of the wireless terminal not designated as improbableis also based on: (ii) the measurement of the location-dependent traitof the radio signal.
 3. The method of claim 1 further comprising:receiving, at the data processing system, a measurement of atmosphericpressure at a location that is outdoors; and wherein designating atleast one of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (ii) the measurement ofatmospheric pressure at the location that is outdoors.
 4. The method ofclaim 1 further comprising: receiving, at the data processing system, ameasurement of temperature at the wireless terminal; and whereindesignating at least one of the plurality of possible lateral locationsof the wireless terminal as improbable is also based on: (ii) themeasurement of temperature at the wireless terminal.
 5. The method ofclaim 4 further comprising: receiving, at the data processing system, ameasurement of temperature at a location that is outdoors; and whereindesignating at least one of the plurality of possible lateral locationsof the wireless terminal as improbable is also based on: (iii) themeasurement of temperature at the location that is outdoors.
 6. Themethod of claim 1 wherein all of the plurality of possible laterallocations of the wireless terminal not designated as improbable areindoors.
 7. A method of estimating the lateral location of a wirelessterminal, the method comprising: receiving, at a data processing system,a measurement of a location-dependent trait of a radio signal asreceived by a wireless terminal; receiving, at the data processingsystem, a measurement of atmospheric pressure at the wireless terminal;designating at least one of a plurality of possible lateral locations ofthe wireless terminal as improbable based on: (i) the measurement ofatmospheric pressure at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the measurement of the location-dependent traitof the radio signal.
 8. The method of claim 7 wherein the step ofestimating the lateral location of the wireless terminal comprises:comparing the measurement of the location-dependent trait of the radiosignal to: (a) a first expected value of the location-dependent trait ofthe radio signal at a first lateral location, and (b) a second expectedvalue of the location-dependent trait of the radio signal at a secondlateral location.
 9. The method of claim 7 further comprising:receiving, at the data processing system, a measurement of atmosphericpressure at a location that is outdoors; and wherein designating atleast one of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (ii) the measurement ofatmospheric pressure at the location that is outdoors.
 10. The method ofclaim 7 further comprising: receiving, at the data processing system, ameasurement of temperature at the wireless terminal; and whereindesignating at least one of the plurality of possible lateral locationsof the wireless terminal as improbable is also based on: (ii) themeasurement of temperature at the wireless terminal.
 11. The method ofclaim 10 further comprising: receiving, at the data processing system, ameasurement of temperature at a location that is outdoors; and whereindesignating at least one of the plurality of possible lateral locationsof the wireless terminal as improbable is also based on: (iii) themeasurement of temperature at the location that is outdoors.
 12. Themethod of claim 7 wherein all of the plurality of possible laterallocations of the wireless terminal not designated as improbable areindoors.
 13. A method of estimating the lateral location of a wirelessterminal, the method comprising: receiving, at a data processing system,a measurement of a difference of a location-dependent trait of: (1) afirst radio signal as received by a wireless terminal, wherein the firstradio signal is transmitted by a first transmitter at a first location,and (2) a second radio signal as received by the wireless terminal,wherein the second radio signal is transmitted by a second transmitterat a second location, and receiving, at the data processing system, ameasurement of atmospheric pressure at the wireless terminal;designating at least one of a plurality of possible lateral locations ofthe wireless terminal as improbable based on: (i) the measurement ofatmospheric pressure at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the measurement of the difference of thelocation-dependent trait; and


14. The method of claim 13 further comprising: receiving, at the dataprocessing system, a measurement of atmospheric pressure at a locationthat is outdoors; and wherein designating at least one of the pluralityof possible lateral locations of the wireless terminal as improbable isalso based on: (ii) the measurement of atmospheric pressure at thelocation that is outdoors.
 15. The method of claim 13 furthercomprising: receiving, at the data processing system, a measurement oftemperature at the wireless terminal; and wherein designating at leastone of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (ii) the measurement oftemperature at the wireless terminal.
 16. The method of claim 15 furthercomprising: receiving, at the data processing system, a measurement oftemperature at a location that is outdoors; and wherein designating atleast one of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (iii) the measurement oftemperature at the location that is outdoors.
 17. The method of claim 13wherein all of the plurality of possible lateral locations of thewireless terminal not designated as improbable are indoors.
 18. A methodof estimating the lateral location of a wireless terminal, the methodcomprising: receiving, at a data processing system, the identity of aradio signal that is received by a wireless terminal; receiving, at thedata processing system, a measurement of temperature at the wirelessterminal; designating at least one of a plurality of possible laterallocations of the wireless terminal as improbable based on: (i) themeasurement of temperature at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the identity of the radio signal.
 19. Themethod of claim 18 further comprising: receiving, at the data processingsystem, a measurement of a location-dependent trait of a radio signal asreceived by the wireless terminal; and wherein estimating the laterallocation of the wireless terminal to be one of the plurality of possiblelateral locations of the wireless terminal not designated as improbableis also based on: (ii) the measurement of the location-dependent traitof the radio signal.
 20. The method of claim 18 further comprising:receiving, at the data processing system, a measurement of atmosphericpressure at a location that is outdoors; and wherein designating atleast one of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (ii) the measurement ofatmospheric pressure at the location that is outdoors.
 21. The method ofclaim 18 further comprising: receiving, at the data processing system, ameasurement of atmospheric pressure at the wireless terminal; andwherein designating at least one of the plurality of possible laterallocations of the wireless terminal as improbable is also based on: (ii)the measurement of atmospheric pressure at the wireless terminal. 22.The method of claim 21 further comprising: receiving, at the dataprocessing system, a measurement of temperature at a location that isoutdoors; and wherein designating at least one of the plurality ofpossible lateral locations of the wireless terminal as improbable isalso based on: (iii) the measurement of temperature at the location thatis outdoors.
 23. The method of claim 18 wherein all of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable are indoors.
 24. A method of estimating the lateral locationof a wireless terminal, the method comprising: receiving, at a dataprocessing system, a measurement of a location-dependent trait of aradio signal as received by a wireless terminal; receiving, at the dataprocessing system, a measurement of temperature at the wirelessterminal; designating at least one of a plurality of possible laterallocations of the wireless terminal as improbable based on: (i) themeasurement of temperature at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the measurement of the location-dependent traitof the radio signal.
 25. The method of claim 24 wherein the step ofestimating the lateral location of the wireless terminal comprises:comparing the measurement of the location-dependent trait of the radiosignal to: (a) a first expected value of the location-dependent trait ofthe radio signal at a first lateral location, and (b) a second expectedvalue of the location-dependent trait of the radio signal at a secondlateral location.
 26. The method of claim 24 further comprising:receiving, at the data processing system, a measurement of atmosphericpressure at a location that is outdoors; and wherein designating atleast one of the plurality of possible lateral locations of the wirelessterminal as improbable is also based on: (ii) the measurement ofatmospheric pressure at the location that is outdoors.
 27. The method ofclaim 24 further comprising: receiving, at the data processing system, ameasurement of atmospheric pressure at the wireless terminal; andwherein designating at least one of the plurality of possible laterallocations of the wireless terminal as improbable is also based on: (ii)the measurement of atmospheric pressure at the wireless terminal. 28.The method of claim 27 further comprising: receiving, at the dataprocessing system, a measurement of temperature at a location that isoutdoors; and wherein designating at least one of the plurality ofpossible lateral locations of the wireless terminal as improbable isalso based on: (iii) the measurement of temperature at the location thatis outdoors.
 29. The method of claim 24 wherein all of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable are indoors.
 30. A method of estimating the lateral locationof a wireless terminal, the method comprising: receiving, at a dataprocessing system, a measurement of a difference of a location-dependenttrait of: (1) a first radio signal as received by a wireless terminal,wherein the first radio signal is transmitted by a first transmitter ata first location, and (2) a second radio signal as received by thewireless terminal, wherein the second radio signal is transmitted by asecond transmitter at a second location, and receiving, at the dataprocessing system, a measurement of temperature at the wirelessterminal; designating at least one of a plurality of possible laterallocations of the wireless terminal as improbable based on: (i) themeasurement of temperature at the wireless terminal; and estimating thelateral location of the wireless terminal to be one of the plurality ofpossible lateral locations of the wireless terminal not designated asimprobable based on: (i) the measurement of the difference of thelocation-dependent trait; and


31. The method of claim 30 further comprising: receiving, at the dataprocessing system, a measurement of atmospheric pressure at a locationthat is outdoors; and wherein designating at least one of the pluralityof possible lateral locations of the wireless terminal as improbable isalso based on: (ii) the measurement of atmospheric pressure at thelocation that is outdoors.
 32. The method of claim 30 furthercomprising: receiving, at the data processing system, a measurement ofatmospheric pressure at the wireless terminal; and wherein designatingat least one of the plurality of possible lateral locations of thewireless terminal as improbable is also based on: (ii) the measurementof atmospheric pressure at the wireless terminal.
 33. The method ofclaim 32 further comprising: receiving, at the data processing system, ameasurement of temperature at a location that is outdoors; and whereindesignating at least one of the plurality of possible lateral locationsof the wireless terminal as improbable is also based on: (iii) themeasurement of temperature at the location that is outdoors.
 34. Themethod of claim 30 wherein all of the plurality of possible laterallocations of the wireless terminal not designated as improbable areindoors.